A Hall effect sensor is a transducer that varies its output voltage in response to a magnetic field. Hall sensor devices can sense a magnetic field perpendicular to a chip in which a Hall plate of the Hall effect sensor is formed. Hall effect sensors can be used for proximity switching, positioning, speed detection, and current sensing applications.
Referring to FIG. 1, the Hall voltage (VH) in a Hall plate 101 is determined by the equation: VH=IB/qnt, wherein “I” represents the current, as depicted by the arrow 103, “B” represents the magnetic field, as depicted by the arrows 105, “q” represents the elementary charge of an electron, “n” represents a doping concentration of the plate 101, as depicted by the + and − symbols 107, and “t” represents the thickness of the plate 101, as depicted by the arrow 109. The sensitivity of a Hall effect sensor can be determined by the Hall voltage equation VH above. An important factor in determining the sensitivity of a Hall effect sensor is high electron mobility.
As illustrated in FIGS. 2A and 2B (top view and cross-sectional view, respectively), a conventional integrated Hall sensor is generally formed by providing a P+ type doping layer 201 in an N well (NW) 203 above a p-type substrate (p-sub) 205 to control the depletion layer in the NW 203. In this instance, N+ type dopant regions 207 are formed at opposite sides of the P+ type doping layer 201 in which a current flows therebetween, as depicted by the arrow 209. Here, the NW 203 is required to be sufficiently deep to accommodate the P+ type doping layer 201, which reduces the sensitivity of the Hall sensor.
Referring to FIGS. 3A and 3B (top view and cross-sectional view along the line 3B-3B′, respectively), another conventional integrated Hall sensor is generally formed by providing a p-type lightly doped drain (MVPLDD) layer 301 in an N well (also referred to as an N+ Hall plate (NH)) 303 between two N+ type dopant regions 305. Additionally, a guard-ring 307 is formed around the N Well 303 and within a P well (PW) 309. Similar to the Hall sensor of FIGS. 2A and 2B, the N well 303 is required to be sufficiently deep to accommodate the MVPLDD layer 301 therein, which again reduces the sensitivity of the Hall sensor.
A need therefore exists for methodology enabling the formation of an integrated Hall effect sensor with a thin Hall plate to enable high sensitivity.